This invention relates in general to sewing machines and in particular to a new and useful device for feeding a strip of material into a sewing machine and sewing it into a cut of fabric.
A device similar to the present invention is disclosed in German No. OS 24 48 887. The device is used in the manufacture of trimmed pockets, for simultaneously sewing in a strip of fabric, the so-called flap. To insert the strip of fabric in a position to start the sewing operation exactly at the edge of the strip, the needle stuck into the fabric is used as a stop for the strip. For this purpose, the needle must be brought, after putting the cut of fabric in place and prior to inserting the strip, from its upper position outside the fabric into its stuck-in low position. To eliminate the necessity of a manual intervention, a photocell unit is provided in the needle zone as a means for controlling the switching function of the sewing machine, which cooperates with a reflective surface of an apparatus for guiding the strip of fabric. Upon inserting the strip of fabric into the guide apparatus, the photocell unit responds to actuate a positioner of the sewing machine and move the needle from its upper into its lower position.
The leading edge of the strip of fabric can be displaced to the stop formed by the needle only upon starting the machine to bring the needle into the low position, and stopping it again. This affects a continuous operation.
With soft strips of fabric, the use of the needle as a stop does not show any disadvantage. It become prohibitive however, as soon as relatively stiff strips are involved, such as strips of paperboard, cardboard, plastic or leather, which are employed in the manufacture of automobile seat slipcovers, for example, since then there is a great chance of deforming the needle. Further sewing with a deformed needle not only can easily lead to erroneous stitches causing time losses in changing the needle, threading again, a mending of the seams, but even the rotary hook may get damaged. Further, the needle stuck in the fabric cannot be used as a stop if the seam is to be started with some backstitches under reversed feed, as is required in most instances, since then the stop must be displaced to some extent beneath and beyond the needle in the forward feed direction.